Calculate RSSI value (signal strength)
Calculation formula:
d = 10^((abs(RSSI) – A) / (10 * n))
Where:
d – calculated distance
RSSI – received signal strength (negative value)
A – signal strength when the transmitter and receiver are 1 meter apart
n – environmental attenuation factor
Suppose we now have three devices [A, E, C] all uploading the signal strength of a certain signal transmitter
The circles intersect at point G, so we can locate G as the location of the signal transmitter.
But sometimes this is not necessarily the case. Due to environmental factors, measurement errors, etc., this situation may occur:
There are two cases where none of them intersect, or only two circles intersect. This is the norm, so I can only use a compromise algorithm:
First, get point G from A to E in proportion [according to the proportion of line segment AE and radius]
Ra/Re Here Ra represents the radius of A, Re represents the radius of E
E(x2,y2) Point E, A(x1,y1) Point A
Vector AE= A-E
Vector AG = Ra/Re * Vector AE
Vector OG= Vector AG+ Vector OA (O represents the origin)
So OG=Ra/Re * Vector AE+ Vector OA
OG =Ra/Re * (x2-x1,y2-y1) + (x1,y1)
So the coordinates of point G are Ra/Re * (x2-x1,y2-y1) + (x1,y1)
After finding the coordinates of point G here, the midpoint W of GC is found according to the same principle. The ratio here is the average value
1/2((Rc/Re)+(Rc/Re)) =Rcg
W = Rcg* (x3-xg,y3-yg) + (xg,yg)
HoneyComm Bluetooth Gateway can be applied into hospital, elderly home, school, prison, office, factory and parking lot etc.
